Golf club designers are constantly manipulating the shape, size, and materials used to manufacture clubs in an effort to maximize performance. For example, fairway woods and hybrids typically have a similar overall mass as a driver, but less than half the volume of a driver. In particular, modern drivers are approximately 460 cc, whereas modern fairway woods range from approximately about 150 to 180 cc. Therefore, manufacturers typically use stainless steel materials for fairway woods and hybrids since the high density of steel provides a desirable mass distribution for the smaller head size. However, the smaller size of the face in fairway woods and hybrids makes it difficult to achieve maximum coefficient of restitution when using stainless steel because the elastic modulus is relatively high, and the face must remain a certain thickness in order not to compromise the durability.
While other lower density materials such as titanium or aluminum-based materials may be used to make the fairway wood, which increases the COR of the club head because of the lower modulus of the material, the low density of the material necessitates additional mass that must be added to meet the target head weight. Indeed, to achieve desirable mass properties in fairway woods, much of the discretionary mass is driven both toward the perimeter and low on the sole with the use of weights hidden within the club head. When made from titanium, the weights must be large and incorporated on the sole to keep the center of gravity (COG) as low as possible. However, the moment of inertia (MOI) (the resistance to twisting of any golf club head when the golf ball is impacted off center) may suffer with such a design and the large concentrated mass in the center of the sole may lead to acoustic issues. While other materials may be used for the weights, the bonding of non-titanium weights to a titanium-based club head is difficult to achieve with dissimilar metals. Alternatively, manufacturers have attempted to use higher density materials such as steel to form the sole of the otherwise titanium-based club head. However, creating a robust metallurgical bond around the perimeter of the steel plate is highly problematic.
Other types of clubs have similar issues. In fact, as drivers have increased in volume, their MOIs have also increased providing “larger sweet spots” and more forgiveness on off-center hits. However, when the volume is maximized through spatially distributing the mass in all three orthogonal orientations, the COG is positioned substantially rearward from the front face of the golf club head and high, which renders shots struck off-center from the sweet spot of the golf club head undesirable as a result of the increase in backspin. And, when weight members are attached to manipulate the COG, the club may become heavy and unwieldy, possibly to the point of limiting a golfer's swing speed and adversely affecting the golfer's swing mechanics. Similarly, efforts to manipulate the distribution of material in a club head with low and high density materials in various portions of the club head may impact the COR of the club head depending on how the material is distributed in the club head.
It would be advantageous to a provide materials for golf clubs that maximize the internal mass distribution and volume of the club head depending on the shape, size, and performance requirements of the particular club head. In addition, it would be beneficial to minimize the elasticity on the face to increase COR while still using a face material that has high strength since the face is a high stress area. Furthermore, there is a need in the art for materials that are capable of being joined to each other via conventional or unconventional methods. The present invention provides materials, golf club heads including the materials, and methods of making the golf club heads that includes the materials to achieve the proper balance between mass distribution and club head performance.